178 Minot: Notes on Histological Technique. III, 2. 



because every one has tried the various recommeudatioiis aud Iias found 

 thera so unsatisfactory that be has tried some modifications, Tliere is 

 bowever a very simple way to obtain a good permanent Solution, 

 namely by making it without animonia. 



Boil one gramme of the best powdered carmine witli 200 cc of 

 water phis an excess of picric acid for half an hour. Allow it to stand 

 and cool; decant the clear fluid, add fresh water, and if necessary 

 picric acid; boil, cool and decant; repeat this Operation until all the 

 carmine is dissolved. Place the decanted fluid in an evapourating dish; 

 add about 1 g thymol, and stand in a warm place until the volume is 

 reduced to 25 cc; let the Solution cool; Alter; wash out the residue, 

 which should be on the filter, with 25 cc water; dilute the filtrate 

 Solution with 50 cc water. By this means a Solution ready for use, 

 which will keep iudefinitely and contaius carmine and picric acid in 

 good proportions, can be prepared with certainty. 



It gives a strenger differential colouring of the tissues, than 

 Ranvier's picrocarmine ; but overstaining must be carefully avoided. 

 For sections hardened in alcohol or with Kleinenbeeg's picro-sulphuric 

 acid two to five minutes are sufficient; for bone, etc. decalcified with 

 picric acid less time, for Müller's fluid specimens considerably more 

 time is required. The fluid stains fibrous connective tissues deep red ; 

 striped muscle deep duU red; smooth muscle, blood and horny tissues, 

 bright yellow; glands reddish yellow; in the kidney it gives a 

 difterential colouration of the various portions of the tubules. 



It gives a quite sharp nuclear colouration , but produces less 

 contrast between the uucleus and the protoplasm than does Ranvieb's 

 picrocarmine. It is however easily made equal and equivalent to the 

 latter by adding very dilute ammonia to the picric acid over Solution 

 until it begins to assume a rieh winc-red shade, which is quite distinct 

 from that of the acid Solution. 



Harvard Medical School, Boston. 

 May 12. 1886. 



